1. Field of the Invention
The present invention relates to a technique for indicating a warning about the temperature of an image sensor.
2. Description of the Related Art
An image capturing apparatus such as a digital camera includes an image sensor such as a CCD or CMOS sensor, and can process an optical image, formed on the image sensor by an optical system, as an image signal by photoelectrically converting the optical image. The obtained image signal is output to a display device of the image capturing apparatus to be displayed (live-view displayed), thereby enabling the display device to function as an electronic viewfinder.
On the other hand, while the display device functions as an electronic viewfinder, the temperature of the image sensor increases due to conversion processing. It is known that as the temperature of the image sensor increases, noise occurs in the photoelectrically converted image signal, thereby causing image quality degradation in a still image captured and obtained immediately after using the display device as an electronic viewfinder.
Japanese Patent Laid-Open No. 2009-033508 discloses a technique for displaying a warning when the temperature of an image sensor exceeds a set limit value, and for forcibly stopping live view display when the temperature reaches a predetermined use limit temperature, in order to prevent image quality degradation in a still image.
However, for a moving image, since a user rarely browses one frame of the moving image for a long time unlike a still image, it is possible to allow some noise caused by a high temperature of the image sensor. That is, the temperature of the image sensor at which it is possible to capture a moving image with image quality degradation unperceivable by the user can be set higher than that at which the user perceives image quality degradation in a still image. Since the display device of the image capturing apparatus used as an electronic viewfinder is typically a low-resolution display device, its allowable noise level is higher as compared with a captured and obtained moving image.
In the technique described in Japanese Patent Laid-Open No. 2009-033508, since live view display is stopped when the temperature of the image sensor reaches a predetermined temperature at which image quality degradation occurs in a obtained still image, live view display does not restart until the temperature of the image sensor falls to a predetermined temperature or below. That is, the user may not be able to capture a moving image while browsing the electronic viewfinder, or to use the electronic viewfinder instead of a telescope.